Method of treating using an over-the-wire EP catheter

ABSTRACT

An over-the-wire electrophysiology catheter which has an emitting electrode on the distal tip electrically connected to a source of high frequency electrical energy. The intravascular device is configured to be advanced through a patient&#39;s cardiac veins or coronary arteries and preferably is also provided with sensing electrodes for detecting electrical activity of the patient&#39;s heart from within a blood vessel of the heart. The device forms large lesions in tissue adjacent to the blood vessel in which the device is located without significantly damaging the blood vessel to effectively terminate signals causing arrhythmia.

This is a continuation of application Ser. No. 08/473,525, which wasfiled on Jun. 7, 1995, now abandoned, which is a divisional of Ser. No.08/447,351, filed May 23, 1995, now U.S. Pat. No. 5,782,760.

BACKGROUND OF THE INVENTION

This invention generally relates to a system for detecting electricalactivity or signals within a patient's heart and particularly fordetermining the source of signals causing arrhythmia from within a bloodvessel of the patient's heart.

Prior methods for treating a patient's arrhythmia include the use ofantiarrhythmic drugs such as sodium and calcium channel blockers ordrugs which reduce the Beta-adrenergic activity. Other prior methodsinclude surgically sectioning the origin of the signals causing thearrhythmia or the conducting pathway for such signals. More frequently,however, to terminate the arrhythmia the heart tissue which causes thearrhythmia is destroyed by heat, e.g. applying a laser beam or highfrequency electrical energy, e.g. RF or microwave, to a desired locationon the patient's endocardium

In the latter instance, the location of the tissue site causing orinvolved with the arrhythmia must be accurately known in order to beable to contact the desired location with a tissue destroying device. Amajor problem of ablating the site of the origin of the signals or aconductive pathway is to accurately determine the location of the siteso that an excessive amount of good tissue is not damaged or destroyedalong with the arrhythmogenic site, while at the same time ensuring thatthe arrhythmia does not return. For example, the average arrhythmogenicsite consists of an area of about 1.4 cm² of endocardial tissue, whereasa re-entrant site might be much larger. RF ablation techniques producelesions about 0.5 cm² in area, so several lesions may be necessary tocompletely ablate an area of interest. If the arrhythmogenic orre-entrant site is not accurately mapped, much good tissue surroundingthe site will be unnecessarily damaged or destroyed.

A variety of prior methods have been used to detect electrical activitywithin a patient's heart to facilitate the mapping of electricalactivity causing the arrhythmia. A number of these prior methods aredisclosed in U.S. Patents which use elongated intravascular signalsensing devices with one or more electrodes on a distal portion of thedevice which are advanced through the patient's vasculature until thedistal portions of the sensing devices are disposed within one or moreof the patient's heart chambers with one or more electrodes in contactwith the endocardial lining. While this procedure is widely used, itdoes not always allow the site of arrhythmogenic signals to beaccurately determined.

In copending application Ser. No. 08/188,619, filed Jan. 27, 1994, nowU.S. Pat. No. 5,509,411, reference is made to intravascular deviceswhich are advanced through a patient's coronary arteries or cardiacveins to desired locations in the patient's epicardium where electricalactivity is detected by means of electrodes on the distal ends of thedevices to locate arrhythmogenic sites or conductive pathways causing orinvolved with arrhythmia. In copending application Ser. No. 08/207,918,filed Mar. 8, 1994, now abandoned, an intravascular device is describedwhich uses RF energy to occlude a blood vessel in order to destroytissue distal to the catheter by creating ischemic conditions therein.

What has been needed is a method and system for accurately detecting thesource of signals which cause the arrhythmia and to create an lesionwhich effectively terminates the arrhythmia without detrimentallyeffecting tissue not involved with the arrhythmia.

SUMMARY OF THE INVENTION

This invention is directed to an elongated intravascular device forcreating a lesion in tissue adjacent a patient's blood vessel fromwithin a patient's blood vessel. The device preferably has means fordetecting electrical activity in adjacent tissue from within the bloodvessel to facilitate accurate placement of the device within the bloodvessel to ensure creating an effective lesion. The device isparticularly suitable for creating a lesion in a patient's heart whichterminates the electrical activity causing an arrhythmia.

The intravascular device of the invention comprises an elongated shaftwith proximal and distal ends, a port in the distal end and a guidewirelumen extending through at least the distal section of the shaft to theguidewire port in the distal section. The distal section of the shaft isconfigured so as to be advanceable through the desired blood vessel orother desired body lumen, such as the patient's coronary arteries orcardiac veins. The device may also be used in blood vessels or otherbody lumens in other parts of the patient's body.

In accordance with the invention, distal shaft section is provided withat least one emitting electrode which is electrically connected by meansof a conductor which extends through the shaft to a high frequencyelectrical energy source exterior to the patient. The emitting electrodeon the distal shaft section preferably forms the distal tip of theelongated shaft and has an inner lumen extending to the port in thedistal end which is a continuation of the lumen extending within theshaft. This allows the intravascular device to be advanced over aguidewire to the desired location within a body lumen where the ablationis to occur.

To form an effective lesion in the tissue adjacent to the body lumenwithout causing unnecessary tissue damage, the temperature of theemitting electrode should be controlled during emission between about70° C. and 100° C. and preferably about 75° C.-85° C.

To effectively cool the electrode, it is preferably provided with one ormore fluid directing passageways which extend radially or longitudinallyto facilitate passage of cooling fluid when the emitting electrode is inoperation. Alternatively, the emitting electrode may be provided with asheath on the exterior thereof which directs cooling fluid along theouter surface to control surface temperatures. The emitting electrodemay be provided with a proximal tubular extension which is secured by asuitable adhesive within the inner lumen extending within the shaft.

In one presently preferred embodiment, a plurality of sensing electrodesare also provided on the distal shaft section proximal to the emittingelectrode so that electrical activity can be detected in tissue adjacentto the body lumen to ensure accurate placement of the emitting electrodewithin the body lumen and effective lesion formation. The sensingelectrodes may be electrically configured for monopolar or multipolaroperative modes. Up to 15 or more sensing electrodes may be providedalong the distal shaft section. The sensing electrodes may have constantor variable electrode spacings and they may be arranged in a first arrayof sensing electrodes with a compact spacing and a second array ofsensing electrodes with a much greater spacing than that in the firstarray. In this latter embodiment, the second array of sensing electrodesmay be used to detect the general location of electrical activity, suchas an arrhythmogenic site or pathway, and then the first array may beutilized to more accurately pinpoint the area of interest based upon thegeneral location detected by the first array of sensing electrode means.The interelectrode spacing in the second array of electrodes should bebetween about 0.25 and about 2 mm, preferably between about 0.5 andabout 1.5 mm, and the interelectrode spacing between the electrodes inthe first array may be about 1 to about 10 mm. When a bipolar ormultipolar mode of sensing is to be used, the spacing between a pair ofbipolar electrodes may be much less than the spacing between pairs ofbipolar electrodes.

The shaft of the intravascular device is preferably formed of aplurality of individually insulated electrical conductors braided orwound into an elongated tubular member with the inner lumen extendingtherein. However, not all of the braided strands which make up thetubular member need be electrical conductors. Some may be high strengthfibers such as nylon, Kevlar® and the like. The insulation on individualelectrical conductors is exposed adjacent to each of the electrodes tofacilitate an electrical connection with the electrode and the electrodemay be secured to the exposed conductor by means of a suitable solder orbrazing material. The sensing electrodes may be secured by their innerperiphery to the underlying tubular member formed of electricalconductors by a suitable adhesive to further ensure maintenance ofelectrical contact between the electrodes and the exposed conductors.

The sensing electrodes may be circular bands about 0.25 to about 1 mm inwidth (the longitudinal dimension when on the device) and are preferablymade from conducting material such as gold which is biocompatible withthe body fluids.

A plastic jacket, preferably a lubricous polymer such as a thermoplasticfluoropolymer, Pebax or a polyethylene may be provided on the exteriorof the shaft with a slight overlap of the jacket over the edges of theindividual electrodes to prevent exposure of a sharp metallic edge whichcan cause damage when the elongated device is advanced through bloodvessels. The entire exterior of an electrode need not be exposed. Forexample, the plastic jacket may be disposed about the distal shaftsection on which the electrodes are mounted and holes may be made in thejacket to expose small portions of the underlying electrodes. Theproximal ends of the electrical conductors connected to the electrodesare electrically connected to one or more multi-pin connectors on theproximal end of the shaft which may be configured to be connected to areceiving member in electrical communication with a video unit which candisplay representations of the electrical activity sensed.

When using the intravascular device of the invention, a guiding catheteris first introduced into the patient's vasculature and advanced thereinuntil the distal tip of the guiding catheter is seated within the ostiumof the coronary sinus or the ostium of a coronary artery. A guidewire isthen advanced through the guiding catheter out the distal end thereofand then directed to a desired venous or arterial branch. Theintravascular device of the invention is advanced over the guidewire tothe desired location where the lesion is to be formed. The sensingelectrodes on the distal section of the intravascular device are used todetect the electrical activity causing or involved with the arrhythmia.Once located, the position of the intravascular device can be adjustedto the extent necessary to place the emitting electrode on the distaltip of the device within the vessel as close as possible to the tissuecausing or involved with the arrhythmia so, when the lesion is formed byemitting high frequency electrical energy, the tissue in question iswithin the lesion.

With the device of the invention, the arrhythmogenic site is accuratelydetected and the lesion formed is large enough to encompass the sitewith little damage to tissue not involved with the arrhythmia so as toeffectively and permanently terminate the arrhythmia. These and otheradvantages of the invention will become more apparent from the followingdetailed description of the invention and the accompanying exemplarydrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of an intravascular device having featuresof the invention wherein an emitting electrode is provided on the distalend of the device for the delivery of high frequency electrical energy.

FIG. 2 is a transverse cross-sectional view of a distal portion of theintravascular device shown in FIG. 1 taken along the lines 2--2.

FIG. 3 is a longitudinal cross-sectional view of a distal portion of analternative embodiment of the invention wherein a plurality of radiallyextending passageways are provided in the emitting electrode to allowfor the passage of cooling fluid.

FIG. 4 is a transverse cross-sectional view of the embodiment shown inFIG. 3 taken along the lines 4--4.

FIG. 5 is a longitudinal cross-sectional view of a distal portion ofanother alternative embodiment of the invention wherein a plurality oflongitudinally extending passageways are provided in the emittingelectrode to allow for the passage of cooling fluid.

FIG. 6 is a transverse cross-sectional view of the embodiment shown inFIG. 5 taken along the lines 6--6.

FIG. 7 is an elevational view, partially in section, of anotheralternative embodiment of the invention wherein a portion of theemitting electrode is provided with an insulating sheath.

FIG. 8 is a transverse cross-sectional view of the catheter shown inFIG. 7 taken along the lines 8--8.

FIG. 9 is an elevational view, partially in section, of anotheralternative embodiment of the invention wherein a sheath is positionedon the exterior of the proximal end of the emitting electrode to directcooling fluid onto the outside of the electrode.

FIG. 10 is a transverse cross-sectional view of the catheter shown inFIG. 9 taken along the lines 10--10.

FIG. 11 is an elevational view, partially in section, of anotheralternative embodiment of the invention wherein an expandable balloon isprovided on one side of the distal section of the device so when it isinflated, the emitting electrode will be urged against the interior ofthe body lumen.

FIG. 12 is a transverse cross-sectional view of the catheter shown inFIG. 11 taken along the lines 12--12.

FIG. 13 is a longitudinal cross-sectional view of another alternativeembodiment of the invention wherein the distal section of the device isprovided with an emitting electrode formed of a coiled wire.

FIG. 14 is a transverse cross-sectional view of the catheter shown inFIG. 13 taken along the lines 14--14.

FIG. 15 is a longitudinal cross-sectional view of an embodiment similarto that shown in FIGS. 13 and 14 but with separate guidewire and fluidlumens.

FIG. 16 is a transverse cross-section of the catheter shown in FIG. 15taken along the lines 16--16.

FIG. 17 is a longitudinal cross-sectional view of the distal section ofanother embodiment of the invention.

FIG. 18 is a transverse cross-sectional view of the embodiment shown inFIG. 17 taken along the lines 18--18.

DETAILED DESCRIPTION OF THE INVENTION

Reference is made to FIGS. 1-2 which schematically illustrate anembodiment of the invention wherein the elongated intravascular device10 includes shaft 11 with a distal section 12 and a proximal section 13and an inner lumen 14 extending within the shaft. The shaft 11 has abraided tubular member 15 formed of a plurality of electrical conductors16. All the strands forming the tubular member 15 need not be conductors16, some may be formed of polymer materials such as nylon or Kevlar®.The distal section 12 of the shaft 11 is provided with an emittingelectrode 17 at the distal tip and a plurality of sensing electrodes 18located proximal to the emitting electrode.

The emitting electrode 17 has a proximal tubular extension 19 whichextends within the inner lumen 14 and is secured by suitable adhesive tothe interior surface of the braided tubular member 15. One or moreindividual insulated electrical conductors 16 are electrically connectedby solder 20 to the emitting electrode 17. Individual insulatedelectrical conductors 16 are also electrically connected to the sensingelectrodes 18 by solder (not shown). The conductors 16 extend to theproximal end of the shaft 11 where they are bundled and formed intocable 21 leading to multiple pin electrical connector 22 where eachelectrical conductor is connected to a separate pin (not shown). Theproximal extremity of the conductor or conductors electrically connectedto the emitting electrode 17 are electrically connected through the pinsto a source of high frequency electrical energy (RF or microwave) andthe proximal extremities of the conductors electrically connected tosensing electrodes 18 are connected through the pins to a display system(not shown) where representations are presented on the signal receivedby the sensing electrodes.

Preferably a safety wire 23 extends within the wall of the shaft 11 andis secured by its distal end to the emitting electrode 17 to prevent itsloss within the patient. The distal extremity 24 of the safety wire 23is coiled within the shaft wall proximal to the emitting electrode 17and is bonded by suitable adhesive 25 to the proximal extension 19. Theproximal end of the safety wire may be secured to the a band (not shown)in the shaft 11 spaced proximal to the emitting electrode 17.

A conventional adapter 27, which is secured to the proximal end of theshaft 11, has a central arm 28 for entry of a guidewire into the innerlumen 14 and a side arm 29 also in fluid communication with the innerlumen 14 for delivery of flushing or cooling fluid to the emittingelectrode 17 on the distal section of the shaft. An O-ring may beprovided in the proximal hub of the central arm 28 to prevent the escapeof fluid.

The embodiment shown in FIGS. 3 an 4 is essentially the same as theembodiment shown in FIGS. 1 and 2 (and is similarly numbered) exceptthat a plurality of radially extending passageways 30 extend between theinner lumen 14 and the exterior of the electrode 17. The guidewire 31,having a core 32 and a coil 33 on the distal extremity of the core, isslidably disposed within the inner lumen 14 and the coil on the distalend of the guidewire extends beyond the passageways 30 and to asignificant extent occludes the inner lumen 14 and reduces considerablythe passage of fluid through the port 34 in the distal tip of theemitting electrode 17. Fluid flowing through the inner lumen 14 willthen be forced to flow through the radial passages 30 thereby coolingthe emitting electrode 17.

Another embodiment is shown in FIGS. 5 and 6 where the emittingelectrode 17 has longitudinally disposed passageways 35 for directingcooling fluid from the inner lumen 14 through the electrode and out theports 36 in the distal tip of the electrode. A tubular sheath 37 formedof a high strength polymer material, such as polyimide, extends betweenthe body of adhesive 25 securing the coiled distal extremity of thesafety wire 24 to the tubular extension 19 of the emitting electrode 17to the proximal end of the electrode to direct fluid which passes fromthe inner lumen 14 through the ports 38 in the tubular extension 19 tothe passageways 35 as indicated by the arrows shown in FIG. 5. Theintravascular device shown is otherwise essentially the same as theprior devices and is similarly numbered. A guidewire 31 may be used toocclude inner lumen 14 as in the prior embodiment to ensure an adequateflow of cooling fluid through passageways 35 to maintain the temperatureof the emitting electrode 17 at a desired level.

FIGS. 7 and 8 illustrate yet another embodiment of the invention whereinan arcuate insulating sheath 40 is secured about an exterior portion ofthe emitting electrode 17 to ensure a more focused emission of highfrequency electrical energy from a smaller exposed portion of theelectrode toward the tissue to be treated to control the size of thelesion formed. This device is for the most part the same as thepreviously discussed embodiments, except for insulation sheath 40, andis therefore similarly numbered.

Another embodiment is depicted in FIGS. 9 and 10 wherein a fluid controlsheath 41 which is secured by its proximal extremity to the adhesive 25and extends over the exterior of the emitting electrode 17. The innerdiameter of the distal end of the sheath 41 is slightly larger than theouter diameter of the electrode 17 to provide an annular gap 42therebetween which directs cooling fluid along the exterior surface ofthe electrode as indicated by the arrows. The cooling fluid passes fromthe inner lumen 14 through the ports 38 in the tubular extension 19 andthrough the annular gap 42. In this embodiment a guidewire 31 isdisposed within the inner lumen 14 with the coil 33 at least partiallyoccluding the distal portion of the inner lumen so that an adequate flowof cooling fluid passes along the exterior of the electrode 17 to ensuresufficient cooling thereof.

In larger blood vessels, it frequently is difficult to maintain contactbetween the emitting electrode 17 and the blood vessel wall. To overcomethis problem, it is desireable to provide an expandable positioningmember, such as an inflatable balloon 43, which when inflated ensurescontact between a desired portion of the blood vessel wall 44 and theemitting electrode 17 as shown in FIGS. 11 and 12. An inflation lumen 45extends through the shaft 11 from its proximal end to a location withinthe interior of the balloon 43. To accommodate for the extra lumen athree arm adapter (not shown) is secured to the proximal end of theshaft. While only one sensing electrode 18 is shown in the drawings, aplurality of sensing electrodes may be provided proximal to the balloon43. The maximum transverse dimension of the balloon 43 as measured fromthe opposite side of the shaft 11 may range from about 0.5 to about 5mm, preferably about 1.5 to about 4 mm.

FIGS. 13 and 14 represent another embodiment where the emittingelectrode 50 is a helical coil on the distal end of the shaft 11. Theproximal end of the coil 51 is secured by solder 52 to the distal end ofthe shaft 11 shown in FIG. 13 to facilitate an electrical connectionwith the conductors 16 in the shaft 11 and the distal end of the coil issecured by adhesive to the enlarged distal end 53 of the lining 54.Perfusion holes 55 are provided in lining 54 to allow fluid passingthrough inner lumen 14 to contact and thus cool the coil 51.

In the embodiment shown in FIGS. 15 and 16 the inner lumen 14 isdisposed within the inner tubular member 60 which extends to the distaltip 61. Annular lumen 62 extends between the interior surface of braidedtubular member 15 and the exterior surface of inner tubular member 60.Electrode coil 63 is secured by its proximal end to the shaft 11 bysolder 64 and is electrically connected to a conductor of the braidedtubular member 15. The distal end of the coil 63 is secured to thedistal tip 61 by a suitable adhesive or by fusing the distal tip aboutthe distal end of the coil. In this embodiment the delivery of coolingfluid through the annular lumen 62 is independent of a guidewire (notshown) in lumen 14.

FIGS. 17 and 18 illustrate the distal portion of yet another embodimentof the invention where an emitting coil electrode 70 is secured to thedistal tip of shaft 11 by means of adhesive or solder. A safety wire 71,which extends through the shaft 11 as in the previous embodiments, issoldered to the distal tip of the emitting coil electrode 70. Sensingelectrodes 18 are provided on shaft 11 proximal to the emittingelectrode coil 70 as in the previous embodiments. The details of shaft11 are the same as shown in the prior embodiments.

The overall length of the intravascular devices of the invention mayrange from about 80 to about 300 cm, typically about 120 to about 175 cmfor delivery through the femoral artery or vein and about 80 to about120 cm for delivery through the brachiocephalic artery or internaljugular vein. Because the intravascular device is to be advanced over aguidewire, the guidewire must be longer than the catheter by about 20 toabout 60 cm. The outer diameter of the shaft of the intravascular deviceshould be less than about 0.065 inch (1.65 mm) and preferably about0.035-0.06 inch (0.89-1.5 mm). The inner lumen 14 has an inner diameterof about 0.01 to about 0.04 inch (0.25-1 mm) to facilitate the receptionand advancement of a guidewire therethrough, which is typically about0.010 to about 0.018 inch (0.25-0.46 mm) in outer diameter. The diameterof the inner lumen through the emitting electrode may be much smallerthan the diameter of the inner lumen in the more proximal portions ofthe shaft 11. The distal section 12 of the shaft is about 3 to about 20cm in length. An intermediate section having an intermediate stiffnessmay be provided between the proximal section 13 and the distal section12 with a length of about 5 to about 40 cm in length, typically about 20cm in length. The radial passageways 30 are typically about 0.02 inch(0.5 mm) in diameter and the longitudinal passageways 35 are typicallyabout 0.01 inch (0.25 mm). The emitting electrode is generally longerthan about 2 mm. For solid electrodes the length is generally less thanabout 10 mm, but for an emitting electrode in the form of helical coilthe length may be about 2 to about 30 mm, preferably about 2 to about 20mm.

To the extent not previously described, the materials of construction ofthe intravascular device of the invention may be formed of conventionalmaterials. The electrical conductors 16 may be electrical grade copperwire about 0.003 inch (0.08 mm) in diameter which are provided with athin insulated jacket or coating of polyimide or other suitableinsulator. The outer jacket may be a thermoplastic polyurethane such asPBAX which is available from Eif Atochem Polymers of Philadelphia, Pa.The jacket of the proximal section is preferably Pebax 1147, the jacketof the intermediate section is Pebax 6333 and the jacket of the distalsection is Pebax 4033. The sensing and emitting electrodes arepreferably formed of an alloy of platinum and iridium, e.g. 90% Pt and10% Ir (wt. %) or of Gold (100%). The safety wire 23 may be a stainlesssteel wire about 0.003 inch (0.08 mm) in diameter with a polyimidecoating. The preferred solder used to join the electrical conductors tothe various electrodes is 95% Sn-5% Ag or 80% Au-20% Sn.

One presently preferred method of using the elongated intravasculardevice includes first advancing a guiding catheter through the patient'svascular system until the distal tip of the guiding catheter is seatedwithin the coronary sinus ostium or the ostium of one of the coronaryarteries. The guiding catheter is torqued by its proximal extremitywhich extends out of the patient to guide the distal tip into theselected ostium. Once the distal end of the guiding catheter is seated,the intravascular device of the invention with a guidewire slidablydisposed within the inner lumen thereof are advanced through the guidingcatheter and out the distal end thereof. The guidewire is first advancedinto the target vein or artery and the intravascular device of theinvention is advanced over the guidewire into the target blood vessel.The sensing electrodes 18 on the intravascular device of the inventionare used to detect electrical activity which allows the physician oroperator to determine the location of the arrhythmogenic focus. When thefocus is located, the intravascular device is moved within the bloodvessel, as required, to position the emitting electrode 17 as close aspossible to the focus. High frequency electrical energy, preferably inthe RF range, is directed through the electrical conductors 16 connectedto the emitting electrode 17 to form the desired lesion whichencompasses the arrhythmogenic focus. Energy levels of about 5 Watts toabout 100 Watts, preferably about 30 Watts to about 70 Watts aresuitable to terminate most arrhythmias. Typical lesions formed are about3 mm to about 20 mm in diameter and about 3 mm to about 20 mm in length.In some instances, where the site of the arrhythmic activity is detectedby other means, an intravascular device may be utilized which does nothave sensing electrodes. For example, the guidewire utilized to advancethe intravascular device of the invention into the desired blood vesselmay be provided with sensing electrodes for detecting the electricalactivity of interest. A suitable device is described in copendingapplication Ser. No. 08/188,619, filed Jan. 27, 1994, which isincorporated herein by reference.

While there are several means described herein to cool the emittingelectrode, a wide variety of means can be used to control thetemperature of the emitting electrode. For example, the electricalenergy to the emitting electrode can be controlled so as to maintain thetemperature thereof. A thermistor or other temperature sensing devicecan be employed to monitor the electrode temperature and the temperaturesensed is used to control in a conventional feedback arrangement theelectrical power delivery.

Although individual features of one embodiment of the invention may bedescribed herein and shown in one or more of the drawings and not inothers, those skilled in the art will recognize that individual featuresof one embodiment of the invention can be combined with any or all thefeatures of another embodiment of the invention. Various modificationsand improvements may be made to the invention without departing from thescope thereof.

What is claimed is:
 1. A method of treating a patient's heartexperiencing arrhythmia comprising:a) providing an intravascularcatheter having an elongated shaft having proximal and distal ends, aport in the distal end, an inner lumen extending within the shaft to theport in the distal end, a distal tip emitting electrode on the elongatedshaft, with at least one lumen extending therethrough in fluidcommunication with the inner lumen of the shaft, and with a port in adistal end of the emitting electrode configured to slidably receive aguidewire therethrough, at least one electrical conductor in electricalcontact with and extending proximally from the emitting electrode andconfigured to be electrically connected to a high frequency electricalenergy source, and a plurality of electrodes on a distal portion of theelongated shaft; b) percutaneously introducing a guidewire into thepatient's vasculature, advancing the guidewire into the coronary sinusor coronary artery of the patient's heart and steering the guidewireinto a branch blood vessel of the coronary sinus or coronary artery; c)positioning the guidewire in the port in the distal end of the emittingelectrode and advancing the intravascular catheter over the guidewire toa desired location within said branch blood vessel; d) detectingelectrical activity within the patient's heart by said plurality ofelectrodes on the distal portion of the intravascular catheter todetermine the location of a source of arrhythmogenic signals or aconducting pathway therefore; e) positioning the intravascular catheterwithin the blood vessel so that the emitting electrode is adjacent tothe location; and f) emitting high frequency electrical energy at leastfrom the emitting electrode to form a lesion within the patient's heartencompassing tissue at said source of arrhythmogenic signals, or in theconducting pathway therefore, said tissue being outside of the bloodvessel in which the intravascular catheter is located.
 2. The method ofclaim 1 wherein the guidewire has a plurality of electrodes, and thestep of detecting the electrical activity includes detecting electricalactivity by the electrodes on the guidewire.
 3. The method of claim 1including controlling the temperature of the emitting electode to lessthan about 100° C.
 4. The method of claim 1 including controlling thetemperature of the emitting electrode by directing cooling fluid fromthe inner lumen of the shaft through at least one lumen in the emittingelectrode.